Impact of mineral oil/water emulsion on clay swelling reduction during drilling

Drilling difficulties through reactive shales have been forced oil companies to use oil-based drilling fluids to stabilize borehole shales and risk completion impairment. On the other hand, drilling with water-based drilling fluid is easy to clean up and substantially increases drilling risks. The development of emulsified drilling fluids has offset some of the undesirable characteristics of water-and oil-based drilling fluids. Although several studies have investigated the possibility of developing invert emulsion-based drilling fluids, without sacrificing the cost-effectiveness of oil-based systems, little attention has been paid to o/w emulsion for reactive shales. This experimental work aims to formulate stable mineral oil/water emulsions and examine their potential to inhibit montmorillonite swelling in aqueous solutions. Numerous stabilities and swelling tests were performed to reach the stated goal, and the results were quantified in terms of the swelling index. A recipe of span 80 and Tween 80 with an HLB value of 10.5 was used to form a stable emulsion. The investigations show that mineral oil/water emulsion increased the performance of water-based mud (WBM) by inhibiting shale hydration.